Display panel or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a display panel or portion thereof with a graphical user interface showing a first image in a sequence of our design;

FIG. 2 is a front view of a display panel or portion thereof with a graphical user interface showing a second image in the sequence of the design; and,

FIG. 3 is a front view of a display panel or portion thereof with a graphical user interface showing a third image in the sequence of the design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-3. The process or period in which one image transitions to another image forms no part of the claimed design.

The outermost broken line rectangle illustrates a display panel or portion thereof that forms no part of the claimed design. All other broken lines illustrate portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display panel or portion thereof with a transitional graphical user interface, as shown and described. 